Thermal State of the Intergalactic Medium at z ∼ 2–4

Telikova, K. N.; Shternin, P. S.; Balashev, S. A.

doi:10.3847/1538-4357/ab52fe

Cited by 21 publications

(21 citation statements)

References 49 publications

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“…T 0 ( × 10 3 K) Our T0 and γ measurements from this statistics are consistent within 1σ with that of Bolton et al (2014); Rorai et al (2018). The γ measurements by Hiss et al (2018); Telikova et al (2019) are in good agreement with our γ measurements. However, their T0 measurements are significantly higher than our measurements at 2.6 ≤ z ≤ 3.6.…”

Section: Comparison With Other Measurementssupporting

confidence: 86%

“…spectra. The lower envelope of the b − log NHI distribution has been used to measure the thermal parameters (Schaye et al 1999;Bolton et al 2014;Gaikwad et al 2017b;Rorai et al 2018;Hiss et al 2018Hiss et al , 2019Telikova et al 2019). Fitting Voigt profiles to Lyα forest spectra is challenging and somewhat subjective.…”

Section: The B-parameter Probability Distribution Function (Bpdf)mentioning

confidence: 99%

“…The lower envelope in the b − log NHI distribution is shown to be sensitive to thermal parameters (Webb & Carswell 1991;Schaye et al 2000;Bolton et al 2014;Gaikwad et al 2017b;Rorai et al 2018). However, the lower envelope method utilizes fewer points that define the lower cutoff in b values at given log NHI (but see Hiss et al 2019;Telikova et al 2019). Recently, Hiss et al (2019) have proposed to use the full b-log NHI 2D distribution to simultaneously measure T0 and γ.…”

Section: The B-parameter Probability Distribution Function (Bpdf)mentioning

confidence: 99%

“…Fitting a lower envelope to the b − log NHI distribution although well motivated, is somewhat subjective. Finding a lower envelope in an objective way is difficult (but see Telikova et al 2019;Hiss et al 2019). The lower envelope is found by iteratively rejecting the lines with low b parameter until convergence is achieved.…”

Section: Comparison With Other Measurementsmentioning

confidence: 99%

“…The thermal parameters of the IGM have been measured by (i) decomposing absorption features into multicomponent Voigt profiles and identifying the lower envelope of the line width (b-parameter) vs H i column density ( NHI; Schaye et al 1999Schaye et al , 2000Bolton et al 2014;Hiss et al 2018;Telikova et al 2019), (ii) measuring the small scale suppression in the transmitted flux power spectrum (Theuns et al 2000;McDonald 2003;Kim et al 2004;Walther et al 2019;Boera et al 2019), (iii) using curvature (defined as, κ = F /[1 + (F ) 2 ] 3/2 where F and F are the first and second derivatives of the normalised flux with respect to the wavelength) statistics (Becker et al 2011;Boera et al 2014;Padmanabhan et al 2015) or (iv) characterising Fourier modes of the flux distribution in the range sensitive to thermal parameters using wavelet analysis (Zaldarriaga 2002;Theuns et al 2002a;Lidz et al 2010;Garzilli et al 2012). Even if the same observational data is used, the sensitivity to small changes in thermal parameters and associated systematic uncertainties are found to be different for different flux statistics (see §5 for a detailed discussion of this).…”

Section: Introductionmentioning

confidence: 99%

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A consistent and robust measurement of the thermal state of the IGM at 2 ≤ z ≤ 4 from a large sample of Ly α forest spectra: evidence for late and rapid He ii reionization

Gaikwad

Srianand

Haehnelt

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We characterise the thermal state of the intergalactic medium (IGM) in ten redshift bins in the range 2 ≤ z ≤ 4 with a sample of 103 high resolution, high S/N Lyα forest spectra using four different flux distribution statistics. Our measurements are calibrated with mock spectra from a large suite of hydrodynamical simulations post-processed with our thermal IGM evolution code cite, finely sampling amplitude and slope of the expected temperature-density relation. The thermal parameters inferred from our measurements of the flux power spectrum, Doppler parameter distribution, as well as wavelet and curvature statistics agree well within their respective errors and all clearly show the peak in temperature and minimum in slope of the temperature density relation expected from He ii reionization. Combining our measurements from the different flux statistics gives T0 = (14750 ± 1322)K for the peak temperature at mean density and a corresponding minimum slope γ = 1.225 ± 0.120. The peak in the temperature evolution occurs around z ≈ 3, in agreement with previous measurements that had suggested the presence of such a peak, albeit with a large scatter. Using cite, we also calculate the thermal state of the IGM predicted by five widely used (spatially homogeneous) UV-background models. The rather rapid thermal evolution inferred by our measurements is well reproduced by two of the models, if we assume (physically well motivated) non-equilibrium evolution with photo-heating rates that are reduced by a moderate factor of ∼0.7 − 0.8. The other three models predict He ii reionization to be more extended with a higher temperature peak occurring somewhat earlier than our measurements suggest.

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Section: Comparison With Other Measurementssupporting

confidence: 86%

Section: The B-parameter Probability Distribution Function (Bpdf)mentioning

confidence: 99%

Section: The B-parameter Probability Distribution Function (Bpdf)mentioning

confidence: 99%

Section: Comparison With Other Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A consistent and robust measurement of the thermal state of the IGM at 2 ≤ z ≤ 4 from a large sample of Ly α forest spectra: evidence for late and rapid He ii reionization

Gaikwad

Srianand

Haehnelt

et al. 2021

Monthly Notices of the Royal Astronomical Society

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The thermal history of the intergalactic medium at 3.9 ≤ z ≤ 4.3

Ondro

Gális

2023

Publ. Astron. Soc. Aust.

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A new determination of the temperature of the intergalactic medium over 3.9 ≤z≤ 4.3 is presented. We applied the curvature method on a sample of 10 high resolution quasar spectra from the Ultraviolet and Visual Echelle Spectrograph on the VLT/ESO.We measured the temperature at mean density by determining the temperature at the characteristic overdensity, which is tight function of the absolute curvature irrespective of γ. Under the assumption of fiducial value of γ = 1.4, we determined the values of temperatures at mean density and for redshift range of 3.9 ≤z≤ 4.1 and 4.1 ≤z≤ 4.3, respectively. Even though the results show no strong temperature evolution over the studied redshift range, our measurements are consistent with an intergalactic medium thermal history that includes a contribution from He ii reionization.

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LYαNNA: A deep learning field-level inference machine for the Lyman-α forest

Nayak,

Walther,

Gruen

et al. 2024

A&A

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The inference of astrophysical and cosmological properties from the Lyman-alpha forest conventionally relies on summary statistics of the transmission field that carry useful but limited information. We present a deep learning framework for inference from the Lyman-alpha forest at the field level. This framework consists of a 1D residual convolutional neural network (ResNet) that extracts spectral features and performs regression on thermal parameters of the intergalactic medium that characterize the power-law temperature-density relation. We trained this supervised machinery using a large set of mock absorption spectra from Nyx hydrodynamic simulations at $z=2.2$ with a range of thermal parameter combinations (labels). We employed Bayesian optimization to find an optimal set of hyperparameters for our network, and then employed a committee of 20 neural networks for increased statistical robustness of the network inference. In addition to the parameter point predictions, our machine also provides a self-consistent estimate of their covariance matrix with which we constructed a pipeline for inferring the posterior distribution of the parameters. We compared the results of our framework with the traditional summary based approach, namely the power spectrum and the probability density function (PDF) of transmission, in terms of the area of the 68<!PCT!> credibility regions as our figure of merit (FoM). In our study of the information content of perfect (noise- and systematics-free) lya forest spectral datasets, we find a significant tightening of the posterior constraints --- factors of 10.92 and 3.30 in FoM over the power spectrum only and jointly with PDF, respectively --- which is the consequence of recovering the relevant parts of information that are not carried by the classical summary statistics.

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Thermal State of the Intergalactic Medium at z ∼ 2–4

Cited by 21 publications

References 49 publications

A consistent and robust measurement of the thermal state of the IGM at 2 ≤ z ≤ 4 from a large sample of Ly α forest spectra: evidence for late and rapid He ii reionization

A consistent and robust measurement of the thermal state of the IGM at 2 ≤ z ≤ 4 from a large sample of Ly α forest spectra: evidence for late and rapid He ii reionization

The thermal history of the intergalactic medium at 3.9 ≤ z ≤ 4.3

LYαNNA: A deep learning field-level inference machine for the Lyman-α forest

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